title: The calculation of the cytoplasmic free [NADP+]/[NADPH] ratio in brain: effect of electroconvulsive seizure.
abstract: This study has investigated the feasibility of calculating the cytoplasmic free [NADP+]/[NADPH] ratio in rat brain. The time course of the change in the substrate ratios of the malate dehydrogenase (decarboxylating) [E.C. 1.1.1.40], NADP+-isocitrate dehydrogenase (decarboxylating) [E.C. 1.1.1.42] and 6-phosphogluconate dehydrogenase (decarboxylating) [E.C. 1.1.1.44] reactions was followed for up to 10 min after a single, unmodified electroconvulsive seizure. From the results it has been concluded that during periods of low flux, the direction and magnitude of the change in the cytoplasmic free [NADP+]/[NADPH] ratio can, in fact, be reasonably determined even though there is some uncertainty in the absolute value of the ratio itself. It is recommended that reliance not be placed on a single enzyme system but that one or both of the other systems also be observed under a given experimental condition to increase confidence in the determination. The results also demonstrate that seizure and anoxia have a far lesser effect on the cytoplasmic free [NADP+]/[NADPH] ratio than on the free [NAD+]/[NADH] ratio in the same compartment. These results suggest that the pathways using the nicotinamide-adenine dinucleotide phosphate system are relatively protected from the rapid fluctuations that seizure and anoxia can produce.
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism*; D002245:Carbon Dioxide / Q000097:blood; D004597:Electroshock; D000860:Hypoxia / Q000378:metabolism; D007521:Isocitrate Dehydrogenase / Q000378:metabolism; D008291:Malate Dehydrogenase / Q000378:metabolism; D008297:Male; D009249:NADP / Q000378:metabolism*; D010084:Oxidation-Reduction; D010734:Phosphogluconate Dehydrogenase / Q000378:metabolism; D051381:Rats; D012274:Ribulosephosphates / Q000378:metabolism; D012640:Seizures / Q000378:metabolism*
chemical_list: D012274:Ribulosephosphates; D002245:Carbon Dioxide; C031524:ribulose 5-phosphate; D009249:NADP; D008291:Malate Dehydrogenase; D007521:Isocitrate Dehydrogenase; D010734:Phosphogluconate Dehydrogenase